The invention relates to an apparatus for air treatment having at least one reservoir which can be filled with a liquid; an air-conveying device; and a contact device which ensures that for the treatment of air to be treated the air comes into contact with the liquid.
The invention further relates to a surface treatment installation, in particular for painting, coating, drying and associated preparation of metallic and nonmetallic objects, having a least one treatment booth, in which there arises exhaust air laden with impurities which is at least partly fed back to the treatment booth in a circuit after prior treatment.
Apparatuses for air treatment of the above-mentioned type are known generally in the prior art, a distinction being made between air humidifiers and air purifiers.
In the case of air humidifiers, three operating principles have become established.
In so-called vaporisers, water situated in the reservoir is heated to boiling and the resulting water vapour is released to the ambient air. In so-called evaporators, water is distributed over a surface as large as possible, over which an air flow is then passed by means of a blower. The evaporation moisture is taken up by this air flow and supplied to the surroundings. Finally, air humidifiers which operate according to the atomiser principle are also known. In these, the water is atomised or nebulised, which can be done, for example, by mechanical turbulence, ultrasound or by means of fine nozzles.
A common feature of these air humidifiers operating according to different principles is that the liquid may reside in the reservoir for quite a long time. If this is the case, germs may multiply in the liquid. In the present context, germs are understood to mean not only bacteria and other protozoa but also fungi and algae.
Given unchecked multiplication, such germs may lead to odour nuisances and serious adverse effects on the health of people who breathe in the humidified air or even only come into contact with it.
Since high germ concentrations of more than 108 germs per cm3 may arise very quickly, biocides, which are understood to mean bactericides and fungicides, are often mixed with the liquids for sterilisation purposes.
Although the germ concentrations can be kept relatively low by such bioactively toxic substances, the costs for this type of sterilisation are high. Moreover, the biocides are additives which are often regarded by users of such air humidifiers as a nuisance in the sense that they cause unnecessary damage to health and/or the environment. A further problem with the use of chemico-biologically active biocides is the ability of numerous germs to develop resistant strains, which can be effectively combated—if at all—only with novel and therefore particularly costly means.
An air humidifier operating according to the vaporiser principle does indeed have the advantage that the water is sterilised by heating, since any germs present in the water are normally killed owing to the high temperature needed to vaporise the water. However, such a vaporiser has a high energy consumption, which is disadvantageous from an economic point of view.
As mentioned at the outset, another type of air treatment consists in air purification. Here, air laden with impurities is passed through water or another suitable purifying liquid in which the impurities readily dissolve. The air thus purified is then fed back to the surroundings by means of a blower. Especially in the case of such an air purifier, the liquid used may become heavily polluted with germs, since it is contaminated increasingly over its period of use by impurities and hence provides a good breeding ground for germs.
The maximum period of use of a liquid in an air purifier depends on its maximum uptake capacity with regard to the impurities to be taken up. Owing to the germ pollution promoted by the contamination of the liquid, however, it is usually necessary to exchange the liquid even before the end of its maximum period of use.
The treatment/purification of exhaust air is particularly relevant in connection with surface treatment installations in which wet separation occurs, as may be the case, for example, in treatment booths of surface treatment installations of the type mentioned at the outset.
The exhaust air discharged from such a treatment booth is contaminated with impurities resulting from the wet separation. Nowadays, both for ecological and economic reasons, a great deal of importance is attached to purifying in a circuit as much as possible of the exhaust air produced in the treatment booth and reusing it. It is therefore desirable to create a surface treatment installation in which an economically acceptable way is found of treating exhaust air for the purpose of recycling.
The present invention is provided to address these and other considerations.